1. Field of the Invention
The present invention relates to an oil pump for use in and attached to a device (for example, chain saw) having an oil-supplied section requiring an oil supply.
2. Description of Related Art
In a chain saw, a saw chain driven by a motor (engine, electric motor, etc.) rotates (runs) at a high speed around a guide bar in contact with the guide bar. Therefore, in the chain saw, there is provided an oil pump that supplies lubricating oil for reducing friction and abrasion between sliding portions of the saw chain and the guide bar. For example, an oil pump disclosed in Japanese Patent Laid-Open Publication No. S64-24180 is configured to supply lubricating oil to a guide rail in such a manner that a pump piston having a gear meshing with a transmission worm driven by a motor moves in an axial direction while rotating in a piston cylinder of a pump case.
An oil pump having such a configuration is often composed to be separated from the transmission worm. That is to say, the transmission worm can be attached to a rotating shaft rotated by the motor, and the oil pump can be attached to the chain saw separately from the transmission worm. Hence, it is necessary that the oil pump is attached to the chain saw so that a center distance between the rotating shaft (transmission worm) and the pump piston (gear) can become an appropriate distance.
Regarding this point, a pump case of an oil pump disclosed in Japanese Patent Laid-Open Publication No. S64-24180 includes, above a pump piston, a cylindrical portion, which is capable of accommodating a transmission worm. Therefore, it may be conceived that, for example, if the cylindrical portion is used for positioning the oil pump to the chain saw, the oil pump can be attached to an appropriate position of the chain saw.
However, the cylindrical portion enlarges the oil pump more than necessary, and moreover, increases weight thereof. In recent years, reduction in size and weight has been required also for the chain saw, and it is also necessary to reduce size and weight of the oil pump for use in and attached to the chain saw. Meanwhile, for example, if the cylindrical portion is removed for the purpose of reducing in size and weight, then it becomes difficult to attach the oil pump to the appropriate position of the chain saw.
Note that such a problem is not limited to the oil pump for use in the chain saw, and can be said to be common to oil pumps for use in a variety of devices, each of which includes the oil-supplied portion requiring an oil supply.
Therefore, it is an object of the present invention to provide an oil pump for use in and attached to a device having an oil-supplied portion requiring an oil supply, the oil pump being capable of ensuring attachment accuracy to the device and achieving the reduction in size and weight.